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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

Posted on 12 July 2011 by Kevin Trenberth

Energy and Climate

Climate change is very much involved with energy, most commonly in the form of heat but other forms of energy are also important. Radiation comes in from the sun (solar radiation at short wavelengths), and every body radiates according to its temperature (proportional to the fourth power of absolute temperature), so that on Earth we, and the surface and atmosphere radiate at infrared wavelengths.

Weather and climate on Earth are determined by the amount and distribution of incoming radiation from the sun. For an equilibrium climate, global mean outgoing longwave radiation (OLR) necessarily balances the incoming absorbed solar radiation (ASR), but with redistributions of energy within the climate system to enable this to happen on a global basis. Incoming radiant energy may be scattered and reflected by clouds and aerosols (dust and pollution) or absorbed in the atmosphere. The transmitted radiation is then either absorbed or reflected at the Earth’s surface. Radiant solar (shortwave) energy is transformed into sensible heat (related to temperature), latent energy (involving different water states), potential energy (involving gravity and altitude) and kinetic energy (involving motion) before being emitted as longwave infrared radiant energy. Energy may be stored, transported in various forms, and converted among the different types, giving rise to a rich variety of weather or turbulent phenomena in the atmosphere and ocean. Moreover the energy balance can be upset in various ways, changing the climate and associated weather.

Hence the incoming radiation may warm up the ground or any object it hits, or it may just go into drying up surface water. After it rains and the sun comes out, the puddles largely dry up before the temperature goes up. If energy is absorbed it raises the temperature. The surface of the body then radiates but also loses heat by transfer through cooler winds or by evaporative cooling. Some energy gets converted into motion as warm air rises and cold air sinks, and this creates winds and thus kinetic energy, which gets dissipated by friction. Over oceans the winds drive ocean currents.

The differential between incoming and outgoing radiation: the net radiation is generally balanced by moving air of different temperature and moisture content around. Air temperature affects density as warmer air expands and thus it takes up more room, displacing cooler air, thereby changing the air in a column whose weight determines the surface pressure. Consequently, this sets up pressure differences that in turn cause winds, which tend to blow in such a way as to try to offset the temperature differences. The Earth’s rotation modifies this simple picture. A result is that southerlies are warm in the northern hemisphere and northerlies are cold. And so we get weather with clouds and rain in all of its wondrous complexity.

The changing seasons illustrate what happens as the sun apparently moves across the equator into the other hemisphere. In summer some excess heat goes into the ocean, which warms up reaching peak values about the equinox, and in winter the land cools off but heat comes out of the oceans and this is carried onto land, and so oceans moderate the seasonal climate variations. Much of the exchange involves water evaporating and precipitating out, and thus the hydrological cycle.

The same can happen from year to year: heat can accumulate in the ocean and then later be released, leading to warmer spells and cooler spells. This commonly happens in the tropical Pacific and gives rise to the El Niño phenomenon. El Niño is the warm phase in the tropical Pacific while La Niña is the cool phase. During and following an El Niño there is a mini global warming as heat comes out of the ocean, while during La Niña, heat tends to get stored in the ocean. The El Niño cycle is irregular but has a preferred time scale of 3 to 7 years.

Ocean heat storage can last longer: for decades or centuries and inevitably involves ocean currents and the much deeper ocean. In the North Atlantic, cold waters sink and move equatorward at depth while the Gulf Stream at the surface takes warmer waters polewards, creating an overturning circulation that can also involve density changes in the ocean associated with both temperature and salt (the thermohaline circulation). Salty water is denser. Nonetheless, much of the ocean overturning circulation is wind driven. The overturning may involve the ocean down to several kilometers and can take many centuries to complete a cycle.

As well as the ocean taking up heat, heat can be lost by forming ice, as glaciers, ice caps, or major ice sheets (Greenland and Antarctica) on land, or as sea ice. Extra heat can melt this ice and may contribute to sea level rise if land ice melts. Surface land can also absorb a small amount of heat but not much and not to great depths as it relies on conduction to move heat through the land unless water is flowing. Land energy variations occur mostly in the form of water or its absence, as heat goes to evaporate surface water. Highest temperatures and heat waves typically occur in droughts or deserts.

The atmosphere can not hold much heat and is dependent for its temperature on links to the underlying surface through conduction and thermals, convection, and radiation, as well as the wind in moving it around.

The global energy budget

In the past, we (Kiehl and Trenberth 1997) provided estimates of the global mean flow of energy through the climate system and presented a best-estimate of the energy budget based on various measurements and models, by taking advantage of the fact that energy is conserved. We also performed a number of radiative computations to examine the spectral features of the incoming and outgoing radiation and determined the role of clouds and various greenhouse gases in the overall radiative energy flows. At the top-of-atmosphere (TOA) values relied heavily on observations from the Earth Radiation Budget Experiment (ERBE) from 1985 to 1989, when the TOA values were approximately in balance.

Values are given in terms of Watts per square meter. The incoming radiation is about 342 W m-2. But there are about 5.1x1014 square meters for the surface area and so the total incoming energy is about 174 PetaWatts (=1015 watts, and so 174 with 15 zeros after it or 174 million billion). About 30% is reflected back to space and so about 122 PW flows through the climate system. For comparison, the biggest electric power plants are of order 1000 MegaWatts, and so the natural flow of energy is 122 million of these power plants. If we add up all of the electric energy generated and add in the other energy used by humans through burning etc, it comes to about 1/9000th of the natural energy flow. Hence the direct effects of human space heating and energy use are small compared with the sun, although they can become important very locally in cities where they contribute to the urban heat island effect.

New observations from space have enabled improved analyses of the energy flows. Trenberth et al. (2009) have updated the earlier global energy flow diagram (Fig. 1) based on measurements from March 2000 to November 2005, which include a number of improvements. We deduced the TOA energy imbalance to be 0.9 W m-2, where the error bars are ±0.5 W m-2 based on a number of estimates from both observations and models.

The net energy incoming at the surface is 161 W m-2, and this is offset by radiation (63), evaporative cooling (80), and direct heating of the atmosphere through thermals (17). Consequently, evaporative cooling and the resulting water cycle play a major role in the energy balance at the surface, and for this reason, storms are directly affected by climate change. The biggest loss at the surface is from long-wave radiation but this is offset by an almost as big downward radiation from greenhouse gases and clouds in the atmosphere to give the net of 63 units.

Updates included in this figure are revised absorption in the atmosphere by water vapor and aerosols. The direct transfer of heat has values of 17, 27 and 12 W m-2 for the globe, land and ocean, and even with uncertainties of 10%, the errors are only order 2 W m-2. There is widespread agreement that the global mean surface upward longwave (LW) radiation is about 396 W m-2, which is dependent on the skin temperature and surface emissivity.

Global precipitation should equal global evaporation for a long-term average, and estimates are likely more reliable of the former. However, there is considerable uncertainty in precipitation over both the oceans and land. The latter is mainly due to wind effects, undercatch and spatial coverage, while the former is due to shortcomings in remote sensing. The downward and net LW radiation were computed as a residual and compared to various estimates which tend to be higher but all involve assumptions and models. The correct depiction of low clouds is a continuing challenge for models and is likely to be a source of model bias in downward LW flux. For example, there are sources of error in how clouds overlap in the vertical and there is no unique way to treat the effects of overlap on the downward flux.

The new observations from space have enabled improved analyses of the energy flows, their variations throughout the annual cycle, for land versus ocean, as a function of location, and also over a number of years. There is an annual mean transport of energy by the atmosphere from ocean to land regions of 2.2±0.1 PW primarily in the northern winter when the transport exceeds 5 PW. It is now possible to provide an observationally based estimate of the mean and annual cycle of ocean energy, mainly in the form of ocean heat content.

Note that the sum of all the values at the TOA and at the surface in the figure leaves an imbalance of 0.9 W m-2, which is causing global warming. As carbon dioxide and other greenhouse gases increase in the atmosphere, there is initially no change in the incoming radiation, but more energy is trapped and some is radiated back down to the surface. This decreases OLR and leads to warming. At the surface the warming raises temperatures and thus increases the surface radiation, but there is still a net amount of energy that partly goes into heating the ocean and melting ice, and some of it goes into increasing evaporation and thus rainfall. To achieve an energy balance, the vertical structure of the atmosphere changes, and the radiation to space ultimately comes from higher regions that were originally colder. In that sense, the figure is misleading because it does not show the vertical structure of the atmosphere or how it is changing.

There is often confusion about how the greenhouse effect works. Greenhouse gases are those with more than two atoms, and water vapor is most important (H2O). But water has a short lifetime in the atmosphere of 9 days on average before it is rained out. Carbon dioxide (CO2), on the other hand, has a long lifetime, over a century, and therefore plays the most important role in climate change while water vapor provides a positive feedback or amplifying effect: the warmer it gets, the more water vapor the atmosphere can hold by about 4% per degree Fahrenheit. Most of the atmosphere is nitrogen (N2) and oxygen (O2) and does not play a role in the greenhouse effect. Oxygen does play an important role through ozone (O3) though, especially in the stratosphere where an ozone layer forms from effects of ultraviolet light. Ozone is not well mixed throughout the atmosphere as it has a short lifetime in parts of the stratosphere, and in the lower atmosphere its life is measured in months as it plays a role in oxidation.

The air is otherwise well mixed up to about 80 km altitude and heavier gases like carbon dioxide do not settle out owing to all the turbulent motions, convection, and so on. Also the other long lived greenhouse gases are well mixed and connect to the non-greenhouse gases with regard to temperature. Air near the surface has a temperature not much less than the surface on average, and therefore it radiates back down with almost as much energy as came up from below. But because the air gets thinner with height, its temperature falls off, and air is a lot colder at 10 km altitude where ‘planes typically fly. This air therefore radiates less both up and down, and the net loss to space is determined by the vertical temperature structure of the atmosphere and the distribution of greenhouse gases.

Changes in energy balance over the past decade

With the new measurements from space, variability in the net radiative incoming energy at the top-of-atmosphere (TOA) can now be measured very accurately. Thus a key objective is to track the flow of anomalies in energy input or output through the climate system over time in order to address the question as to how variability in energy fluxes is linked to climate variability. The main energy reservoir is the ocean (Fig. 2 below), and the exchange of energy between the atmosphere and ocean is ubiquitous, so that heat once sequestered can resurface at a later time to affect weather and climate on a global scale. Thus a change in the energy balance has consequences, sooner or later, for the climate. Moreover, we have observing systems in place that nominally can measure the major storage and flux terms, but due to errors and uncertainty, it remains a challenge to track anomalies with confidence.

Figure 2. Energy content changes in different components of the Earth system for two periods (1961–2003 and 1993–2003). Blue bars are for 1961 to 2003; burgundy bars are for 1993 to 2003. Positive energy content change means an increase in stored energy (i.e., heat content in oceans, latent heat from reduced ice or sea ice volumes, heat content in the continents excluding latent heat from permafrost changes, and latent and sensible heat and potential and kinetic energy in the atmosphere). All error estimates are 90% confidence intervals. No estimate of confidence is available for the continental heat gain. Some of the results have been scaled from published results for the two respective periods. From (IPCC 2007, Fig. TS.15 and Fig. 5.4).

A climate event, such as the drop in surface temperatures over North America in 2008, is often stated to be due to natural variability, as if this fully accounts for what has happened. Aside from weather events that primarily arise from instabilities in the atmosphere, natural climate variability has a cause. Its origins may be external to the climate system: a change in the sun, a volcanic eruption, or Earth’s orbital changes that ring in the major glacial to interglacial swings. Or its origins may be internal to the climate system and arise from interactions among the atmosphere, oceans, cryosphere and land surface, which depend on the very different thermal inertia of these components.

El Niño

As an example of natural variability, the biggest El Niño in the modern record by many measures occurred in 1997-98. Successful warnings were issued a few months in advance regarding the unusual and disruptive weather across North America and around the world, and were possible in part because the energy that sustains El Niño was tracked in the ocean by a new moored buoy observing system in the Tropical Pacific. Typically prior to an El Niño, in La Niña conditions, the cold sea waters in the central and eastern tropical Pacific create high atmospheric pressure and clear skies, with plentiful sunshine heating the ocean waters. The ocean currents redistribute the ocean heat which builds up in the tropical western Pacific Warm Pool until an El Niño provides relief. The spread of warm waters across the Pacific in collaboration with changing winds in turn promotes evaporative cooling of the ocean, moistening the atmosphere and fueling tropical storms and convection over and around the anomalously warm waters. The changed atmospheric heating alters the jet streams and storm tracks, and influences weather patterns for the duration of the event.

The central tropical Pacific SSTs are used to indicate the state of El Niño, as in Fig. 3 presented below. In 2007-08 a strong La Niña event, that spilled over to the 2008-09 northern winter, had direct repercussions for cooler weather across North America and elsewhere. But by June 2009, the situation had reversed as the next El Niño emerged and grew to be a moderate event, with temperatures in the top 150 m of the ocean above normal by as much as 5°C across the equatorial Pacific in December 2009. Multiple storms barreled into Southern California in January 2010, consistent with expectations from the El Niño. The El Niño continued until May 2010, but abruptly reversed to become a strong La Niña by July 2010.

Figure 3. Recently updated net radiation (RT=ASR-OLR) from the TOA http://ceres.larc.nasa.gov/products.php?product=EBAF. Also shown is the Niño 3.4 SST index (green) (left axis); values substantially above the zero line indicate El Niño conditions while La Niña conditions correspond to the low values. The decadal low pass filter is a 13 term filter making it similar to a 12-month running mean. Units are Wm-2 for energy and deg C for SST.

We can often recognize these changes once they have occurred and they permit some level of climate forecast skill. But a major challenge is to be able to track the energy associated with such variations more thoroughly: where did the heat for the 2009-10 El Niño actually come from? Where did the heat suddenly disappear to during the La Niña? Past experience suggests that global surface temperature rises at the end of and lagging El Niño, as heat comes out of the Pacific Ocean mainly in the form of moisture that is evaporated and which subsequently rains out, releasing the latent energy.

The values and patterns of SSTs in the northern summer of 2010 undoubtedly influenced the extremes of weather, from excessive rains and flooding in China, India and Pakistan, the active hurricane season in the Atlantic, and record breaking rains in Colombia. Later the high SSTs north of Australia contributed to the Queensland flooding. The La Niña signature has also been present across the United States in the spring of 2011 with the pattern of drought in Texas and record high rains further to the north, with flooding along the Mississippi and deadly tornado outbreaks.

Anthropogenic climate change

The human influence on climate, arising mostly from the changing composition of the atmosphere, also affects energy flows. Increasing concentrations of carbon dioxide and other greenhouse gases have led to a post-2000 imbalance at the TOA of 0.9±0.5 W m-2 (Trenberth et al. 2009) (Fig. 1), that produces “global warming”, or more correctly, an energy imbalance. Tracking how much extra energy has gone back to space and where this energy has accumulated is possible, with reasonable closure for 1993 to 2003; see Fig. 2. Over the past 50 years, the oceans have absorbed about 90% of the total heat added to the climate system while the rest goes to melting sea and land ice, and warming the land surface and atmosphere. Because carbon dioxide concentrations have further increased since 2003 the amount of heat subsequently being accumulated should be even greater.

While the planetary imbalance at TOA is too small to measure directly from satellite, instruments are far more stable than they are absolutely accurate. Tracking relative changes in Earth’s energy by measuring solar radiation in and infrared radiation out to space, and thus changes in the net radiation, seems to be at hand. This includes tracking the slight decrease in solar insolation from 2000 until 2009 with the ebbing 11-year sunspot cycle; enough to offset 10 to 15% of the estimated net human induced warming.

In 2008 for the tropical Pacific during La Niña conditions, extra TOA energy absorption was observed as expected; see Fig. 3. The Niño 3.4 SST index is also plotted on this figure and the slightly delayed response of the OLR to cooler conditions in the record and especially in 2008 is clear. However, the decrease in OLR with cooler conditions is accompanied by an increase in ASR as clouds decrease in amount, leaving a pronounced net heating (>1.5 W m-2) of the planet in the cooler conditions. And so this raises the question as to whether a coherent perspective that accounts for both TOA and ocean variability can be constructed from the available observations. But ocean temperature measurements from 2004 to 2008 suggested a substantial slowing of the increase in global ocean heat content, precisely during the time when satellite estimates depict an increase in the planetary imbalance.

Since 1992, sea level observations from satellite altimeters at millimeter accuracy reveal a global increase of ~3.2 mm yr-1 as a fairly linear trend, although with two main blips corresponding to an enhanced rate of rise during the 1997-98 El Niño and a brief slowdown in the 2007-08 La Niña. Since 2003, the detailed gravity measurements from Gravity Recovery and Climate Experiment (GRACE) of the change in glacial land ice and water show an increase in mass of the ocean. This so-called eustatic component of sea level rise may have compensated for the decrease in the thermosteric (heat related expansion) component. However, for a given amount of heat, 1 mm of sea level rise can be achieved much more efficiently – by a factor of 40 to 70 typically – by melting land ice rather than expanding the ocean. So although some heat has gone into the record breaking loss of Arctic sea ice, and some has undoubtedly contributed to unprecedented melting of Greenland and Antarctica, these anomalies are unable to account for much of the measured TOA energy (Fig. 4). This gives rise to the concept of “missing energy” (Trenberth and Fasullo 2010).

Figure 4. The disposition of energy entering the climate system is estimated. The observed changes (lower panel; Trenberth and Fasullo 2010) show the 12-month running means of global mean surface temperature anomalies relative to 1901-2000 from NOAA (red (thin) and decadal (thick)) in °C (scale lower left), carbon dioxide concentrations (green) in ppmv from NOAA (scale right), and global sea level adjusted for isostatic rebound from AVISO (blue, along with linear trend of 3.2 mm/yr) relative to 1993, scale at left in millimeters). From 1992 to 2003 the decadal ocean heat content changes (blue) along with the contributions from melting glaciers, ice caps, Greenland, Antarctica and Arctic sea ice plus small contributions from land and atmosphere warming (red) suggest a total warming for the planet of 0.6±0.2 W m-2 (95% error bars). After 2000, preliminary observations from TOA (black) referenced to the 2000 values, as used in Trenberth and Fasullo (2010), show an increasing discrepancy (gold) relative to the total warming observed (red). The quiet sun changes in total solar irradiance reduce the net heating slightly but a large energy component is missing (gold). Adapted from Trenberth and Fasullo (2010). The monthly global surface temperature data are from NCDC, NOAA: http://www.ncdc.noaa.gov/oa/climate/research/anomalies/index.html ; the global mean sea level data are from AVISO satellite altimetry data: http://www.aviso.oceanobs.com/en/news/ocean-indicators/mean-sea-level/ ; and the Carbon dioxide at Mauna Loa data are from NOAA http://www.esrl.noaa.gov/gmd/ccgg/trends/.

To emphasize the discrepancy, Fig. 5 presents an alternative version of Fig. 2 for 1992 to 2003, as a contrast to 2004 to 2008. The accounting for all terms and the net imbalance is compatible with physical expectations and climate model results, with the net imbalance about 0.7 W m-2 at TOA for 1992 to 2003. However, for the 2004 to 2008 period, the decrease in solar radiation associated with the sunspot cycle and the quiet sun in 2008 contributed somewhat, but the Ocean Heat Content (OHC) change is a lot less than in the previous period and a residual imbalance term: the missing energy, is required.

Figure 5. The energy entering the climate system is estimated for the various components: warming of the atmosphere and land, ocean heat content increase, melting of glaciers and ice caps (land ice), melting of the major ice sheets (Greenland and Antarctica), and changes in the sun. For 1993 to 2003 these are summed to give the total which is equivalent to about 0.7 W m-2. For 2004-2008, TOA measurements are used to provide an increment to the total based on comparisons with 2000-2003, and the quiet sun has contributed, but the sum is achieved only if a spurious residual is included. Units are 1020 Joules/year.

Further inroads into this problem will no doubt become possible as datasets are brought up to date and refined. In the meantime, we have explored the extent to which this kind of behavior occurs in the latest version of the NCAR climate model. In work yet to be published (it is submitted), we have found that energy can easily be “buried” in the deep ocean for over a decade. Further preliminary exploration of where the heat is going suggests that it is associated with the negative phase of the Pacific Decadal Oscillation and/or La Niña events.

Clearly, tracking energy and how and where it is stored, and then manifested as high SSTs which in turn affect subsequent climate is an important thing to do.

In 1998 Karl and Knight reported that from 1910 to 1996 total precipitation over the contiguous U.S. increased, and that 53% of the increase came from the upper 10% of precipitation events (the most intense precipitation). The percent of precipitation coming from days of precipitation in excess of 50 mm has also increased significantly.

Studies by Pruski and Nearing indicated that, other factors such as land use not considered, we can expect approximately a 1.7% change in soil erosion for each 1% change in total precipitation under climate change. The removal by erosion of large amounts of rock from a particular region, and its deposition elsewhere, can result in a lightening of the load on the lower crust and mantle. This can cause tectonic or isostatic uplift in the region. Research undertaken since the early 1990s suggests that the spatial distribution of erosion at the surface of an orogen can exert a key influence on its growth and its final internal structure (see erosion and tectonics).

00

Moderator Response: [muoncounter] Hot-linked; however, this has nothing to do with the topic of this thread. Please stay on topic.

You show the net radiation increasing significantly after 2005. This is based on satellite measurements, right?

What is changing? The increase seems to early to me to be solar cycle 24, so I presume the difference is either a change in albedo and/or a reduction in OLR. Are there numbers for each of these? Are they in accord with changes in e.g. atmospheric composition?

Muoncounter #3: If there is an increase in the net energy budget, then either more energy is coming in or less is going out. If it's not the sun, then doesn't that leave either albedo (changing the absorption of incoming radiation) or greenhouse effect (changing the outgoing radiation)? What else is there?

The change in figure 4a is not small: The difference in net energy flux from 2000 to 2009 in figure 4a is nearly 1W/m^2, and half of that in the last 2 years. That's equivalent to adding ~80ppm of CO2! Can weather cause fluctuations that big, or is it change in natural or anthropogenic forcing?

Dean, Fig 19 relates to Von Schuckmann & Le Traon 2011 who find that the upper ocean from 2005-2010 has warmed significantly. I'm writing up a post on it at the moment. It doesn't resolve the 'missing heat', but rather closes the gap a little - down to a .59W/m2 imbalance.

Hansen suggests that the shielding effect of aerosols may be greater than anticipated, and that the climate models match 20th century observations in that they underestimate the strong cooling effects of aerosols, but overestimate the ocean response because they mix heat too quickly down into the ocean, compared to chemical tracer observations.

Dean, if one accepts Hansen is correct and that there is no 'missing heat' in the ocean because the models are wrong, then yes there is no imbalance. He could be right - but seems a bit light on evidence at the moment. On the other hand the warming found by Von Schuckmann & Le Traon is a bit more than that found in other recent analysis, so it does 'close the gap a little'.

As for sulfates, although they do tend to wash out of the atmosphere within weeks to months, they can have a profound effect on cloud formation - the finer particles seeding smaller, but more numerous cloud 'droplets' - for want of a better word. Being smaller they are less likely to condense into rain, and they also make clouds more effective mirrors. So more sunlight is reflected back out to space. This effect is greater is the dry seasons, when sulfates are less prone to being 'washed out'.

If Hansen is correct, this affects the energy budget because less energy is being received at the Earth's surface (there's far less incoming energy to account for). The climate models use an estimate of the aerosol cooling effect in their simulations, but if the ocean mixing rate is wrong in models (i.e. too efficient), the model match with 20th century observations is simply fortuitous.

Seems a stretch. One would expect the budget doesn't balance for a number of reasons, the large uncertainty in measurements being a significant one, but also a greater aerosol cooling, deep ocean mixing and increased radiation to space (Katsman & Oldenburgh (2011)

A better link for Kaufmann courtesy of WUWT. From quick look, it uses Kaufmann's 2006 statistical model to relate forcings to temperature but with update forcing data including the new aerosol data which is up. Hansen also states "Global warming has been limited, as aerosol cooling partially offsets GHG warming" and argues that aerosols are understated in the models.
Kaufmann cannot rule out natural variability but I think the Argo network will eventually make this clearer.

Here we see real skepticism at work in science. Hansen has proposed that aerosols reflect more heat into space. Trenberth proposes that the missing heat has been absorbed into the deep ocean. Hansen is skeptical of Trenberth's results and Trenberth is skeptical of Hansen. Both of them will marshall their data to determine which is more correct (it may be a combination of both effects). In the end the data will determine who is correct. This is an example of real climate scientists debating the data.

Both Trenberth and Hansen agree that strong action is needed to counter the problems caused by BAU.

The question that comes to my mind after reading this excellent article, and the discussion above, is this:

How does this affect model predictions for the next century?

If Dr Trenberth is correct, that there is a decadal-scale sequestration of heat in the deep ocean, then this would, I presume, result in larger, decadal-scale oscillations in global temperature superimposed on the upward trend. It would appear that we're in a 'cool' period at the moment, which leads to the obvious conclusion that some time in the next few years to a decade or, we might see a very dramatic upward swing in global surface temperatures, as that deep ocean heat storage temporarily slows or even reverses.

On the other hand, if Dr Hansen is correct, then as aerosols are scrubbed from more developing world power stations, we might see a similar upward surge in temperatures as the aerosol effects reduce.

Either way, the next decade or two could see substantial surface temperature rises, but how would it affect temperatures later in the century? Would either of these options significantly change global climate model predictions of the long-term trend over that timescale? And if so, in which direction?

"I know they provide 333 W/sq metre "back radiation" but where do these joules come from to heat the atmosphere to the level where it radiates more than the incoming solar radiation?"

If you read the tables in the paper, it's not really 'back radiation' but downward LW radiation received at the surface. Why he refers to this as 'back radiation' I don't know. The fundamental problem is downward LW at the surface has three potential sources: Some of it last originated from surface emitted LW, some of it last originated from the Sun absorbed by the atmosphere yet to reach the surface, and some of it last originated from the kinetic energy moved from the surface into the atmosphere while also radiates in the LW infrared.

The term 'back radiation' generally implies downward emitted LW that last originated from surface emitted. The diagram makes it look like of the 396 W/m^2 emitted at the surface, 333 W/m^2 are coming back from the atmosphere, which is why it's confusing.

"Um, I think "back radiation" is radiation emitted from the atmosphere that strikes the surface. I cant see how "last originated from surface emitted" can make any kind of sense.

It's a key distinction because the amount that last originated from the surface is what is actually determining the net surface energy flux, which is what ultimately is determining the surface temperature.

A lot of the downward emitted LW is 'forward radiation' that last originated from the Sun, yet to reach the surface. Also, the kinetic energy (latent heat and thermals) moved from the surface into the atmosphere is in addition to the radiative flux at the surface, so any amount from it radiated back to the surface also did not last originate from surface emitted of 396 W/M^2, which is the just net energy flux at the surface (in the steady-state at least).

I also dispute the way the diagram depicts 78 W/m^2 of the post albedo as being 'absorbed by the atmosphere' without ultimately getting the surface somehow. I certainly don't dispute that some of the post albedo is absorbed by the atmosphere (mostly clouds), but if any of this energy finds it's way radiated out to space without ever reaching the surface, it's trading off energy from the surface absorbed by clouds that would otherwise have be leaving the system at the TOA. Indirectly one way or another, the full post albedo has to get to the surface if COE is to be satisfied. The numbers don't work unless it does.

Also, where is the return path of latent heat in the form of precipitation in the diagram? Surely, not all of it returns to the surface in the form of downward LW.

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Response:

[DB] Please do not rehash the entirety of the 2nd Law thread. You were painstakingly corrected there, many times, by patient commentators.

A lot of the downward emitted LW is 'forward radiation' that last originated from the Sun, yet to reach the surface.

You need to quantify this, or, if you're too lazy, just point us to whatever denialist screed has raised the issue. Because hopefully they'll have quantified "a lot", and, of course (!), thereby prove that it's not coming from the GHG mechanism, proving some modern physics false, etc, etc ...

I am unsure where the question of the missing heat is, R. S. Knox, David H. Douglass 2010; (Recent energy balance of Earth International Journal of Geosciences, 2010) is quite sufficient for explanation of the complexity.

RW1 - Sorry, this is weird. It sounds like you are thinking of this as photons being little balls bouncing around with a "history" of where that have been. Instead, this is a series of energy balances reflecting all energy transfer processes. Its unphysical to try and track a photon "history".

It would be very interesting to hear what Kevin have to say about the sulfur situation and possibilities of tracking the heat in the ocean with todays measurement systems...
i.e.
articles linked in comment 23 and 7.

And I guess this also comes in to play:
http://www.springerlink.com/content/akh241460p342708/
we estimate that up to one third of the late twentieth century warming could have been a consequence of natural variability.

One thing I don't understand is short term variability in GAT, for example, in the first column here: http://vortex.nsstc.uah.edu/data/msu/t2lt/uahncdc.lt Looking at that first column, there is a clear AGW and clear ENSO response. But there is also a month-to-month variability that can be as much as 0.1 or 0.2 This variability even tracks down to the day timeframe although that is more unusual. My question is, is there an energy transfer with the ocean over such short time intervals, or is it just lost to space and regained later?

"the exchange of energy between the atmosphere and ocean is ubiquitous, so that heat once sequestered can resurface at a later time to affect weather and climate on a global scale"

I'm missing a more in depth part about the atmosphere/hydrosphere interconnection - how the changing weathering process affects land mass and flux of heat content therein.

"although some heat has gone into the record breaking loss of Arctic sea ice, and some has undoubtedly contributed to unprecedented melting of Greenland and Antarctica, these anomalies are unable to account for much of the measured TOA energy (Fig. 4). This gives rise to the concept of “missing energy” "

Could this indicate an uptake of permafrost melt and other such processes, increase of weathering-erosion of the pedoshere? In the sense that decomposition of organic materials, the soil permafrost environment transition into a more fluid "unstable" state, could account for the missing heat?

Interesting, Human. As a soil science person, I wondered about the energy difference between the top 10 meters of soil with, and without, groundwater. By my hypothesis, drought can mask the energy calculations. Unsure. Connolly says this dwarfed by oceans, if I read him correctly.

I was reading a thing by a denier and he seemed confused about energy in / out. I immediately thought of the quartz or glass tubes around kerosene heaters. The energy outflow is retarded and the catalytic metal sleeve becomes red hot; hotter than it would without the glass tube. Yet energy output is the same. (except for the catalysis itself!) The point is, even with much more retained heat, the net outflow will quickly reach equilibrium. I suppose I should have pointed that out to the denier.

Re #28, part of the top soils are "rocks" which too react with thermal energy.

Thermal stress weathering (sometimes called insolation weathering)results from expansion or contraction of rock, caused by temperature changes. Thermal stress weathering comprises two main types, thermal shock and thermal fatigue. Thermal stress weathering is an important mechanism in deserts, where there is a large diurnal temperature range, hot in the day and cold at night. The repeated heating and cooling exerts stress on the outer layers of rocks, which can cause their outer layers to peel off in thin sheets. Forest fires and range fires are also known to cause significant weathering of rocks and boulders exposed along the ground surface. Intense, localized heat can rapidly expand a boulder. Although temperature changes are the principal driver, moisture can enhance thermal expansion in rock too. Pedology

"Here we see real skepticism at work in science. Hansen has proposed that aerosols reflect more heat into space. Trenberth proposes that the missing heat has been absorbed into the deep ocean. Hansen is skeptical of Trenberth's results and Trenberth is skeptical of Hansen. Both of them will marshall their data to determine which is more correct (it may be a combination of both effects). In the end the data will determine who is correct. This is an example of real climate scientists debating the data."

Probably the two most prominent climate scientists on the planet disagree about whether or not the warming imbalance is 0.9W/sq.m or 0.59W/sq.m over the last 5-6 years when the imbalance must in theory be increasing due to increased CO2GHG in the atmosphere.

Dr Trenberth says the missing heat 'is there but we just can't yet measure it in the oceans' and Dr Hansen says the heat 'is not there because extra aerosols have reflected it out to space'.

This seems to be a fundamental difference in how the trajectory of warming might evolve - as we could not expect Asian aerosols to disappear anytime soon.

Dr Trenberth wrote:

"While the planetary imbalance at TOA is too small to measure directly from satellite, instruments are far more stable than they are absolutely accurate. Tracking relative changes in Earth’s energy by measuring solar radiation in and infrared radiation out to space, and thus changes in the net radiation, seems to be at hand."

The CERES satellite data quoted in the Aug09 paper for 2000-05 were adjusted to an estimated imbalance of 0.9W/sq.m from an absolute value of about +6.4W/sq.m.
The latest data shown in Fig 3 above shows an Rt value varying around the 1.0W/sq.m. How is this data 'adjusted' from the absolute value?

I would also like to ask Dr Trenberth whether the ENSO-La Nina cycles are 'internal' redistributions of global heat already within the system or are external global forcings which should be added to the RF and climate response terms to determine an imbalance.

The final issue I query is how Dr Trenberth's 'missing heat' gets into the deep oceans in a relatively short few years. viz. "The overturning may involve the ocean down to several kilometers and can take many centuries to complete a cycle".

You might be surprised on that one. The rate of change on almost every level in society in China is very rapid. The clean air act in the US had a pretty rapid affect on air pollution here. There is no reason to believe that China's responses to air pollution will be any slower.

Nice post between the two theories. There may be other explanations for where the heat went, or why the heat has not reached the surface, which may be revealed when the data materializes. However, it does come down to two basic interpretations: either the heat is there, and we are just not measuing it (Trenberth), or the heat is not (Hansen).

Eric (Skeptic) @ 25 - I've been thinking along the same lines. The year-to-year variability in OHC is large, even in the ARGO data,, too large to accommodate the small rise in air temperatures we observe during El Nino. So what's happening to that heat?, is it being lost to space as Katmsan and Oldenburgh (2011) suggest?

[DB] I deleted your previous comment as it was a rehash of material you had previously submitted - and been responded to - on the 2nd Law thread. That you didn't like the answers you were given does not obviate the fact that you were indeed given answers to your questions there.

Typically, comments challenging the moderation policy are summarily deleted, as posting here at SkS is a privilege; thus the act of posting here is then tacit agreement to comply with the Comments Policy. And repetitive posting is a violation of that policy.

“Extensive evidence exists from previous long control simulations showing simulated climate possesses large-scale variations on decadal to centennial timescales (Delworth et al., 1993; Delworth and Mann, 2000; Latif et al., 2004; Knight et al., 2005). Typically, these variations are associated with the principal modes of decadal variability of the climate system – the Atlantic Multidecadal Oscillation (AMO) (Enfield et al., 2001) and the Pacific Decadal Oscillation (PDO), sometimes referred to as the Interdecadal Pacific Oscillation (IPO) (Power et al., 1999). The AMO is a North Atlantic-centred mode in which sea surface temperatures (SSTs) vary coherently within the basin on multidecadal to centennial timescales, and which can have far reaching climate impacts (Knight et al., 2006). The PDO/IPO has a characteristic pattern of anomalously warm and cool SSTs in the Pacific Ocean that resembles a modified El Ni˜no pattern, and typically has a shorter timescale of about two decades (Kwon and Deser, 2007). So-called “perfect model” experiments (Collins and Sinha, 2003), in which sections of model control simulations are repeated after small initial perturbations, demonstrate the potential for multidecadal oceanic processes to provide a long-term memory of the initial state.”

... and ending with this sentence:

“Future work may explore the response of extra ensemble members which start from deliberately chosen high or low AMO states.”

Maybe in a much larger change in energy content in the ocean is responsible underestimated AMO? But then earlier (195? -1999) energetic "effect anthropogenic" would be considered too highly estimated ...

Do we have any indicaton that Dr Trenberth will participate in discussions on this thread?

There are a number of questions which merit some response (and a few which do not), so if there is no one arguing Dr Trenberth's case (chiefly himself) - this thread will wither on the vine.

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Response:

[DB] My understanding was that Dr. Trenberth was travelling abroad for a few weeks. As a service, he provided this article before he left. Given his busy schedule, I would be (happily) surprised if he were able to make an appearance before then.

That being said, perhaps few feel the need to prosecute the case so eloquently presented by an expert, such as Dr. Trenberth?

In any event, questions remaining unanswered should be addressed in a future iteration of this article, so tack any of them up here for posterity. Few threads here at SkS are truly "withered"; many are inactive, but witness the undead 2nd law thread...

Rob #35, if the weather causes a 0.1 or 0.2 rise or fall in GAT in less than a week (although this only happens a few times a year), it is probably one of the more random effects of weather (using a precise definition of random). For this to happen, with either outcome cooling or warming, a lot of weather systems have to complement in both hemispheres which are, for the most part uncoupled. Getting both hemispheres to line up on a short time scale is thus pure chance. Getting a single hemisphere to align in warming or cooling is a little less random due to teleconnections, but those are limited in scope and generally peristent through a season. The topic certainly merits a lot more research.

BTW, it's my understanding that Trenberth is traveling around AU/NZ and will return on the 21'st.

G

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Moderator Response: [Dikran Marsupial] Posts containing complaints about moderation are normally deleted (after reading), so it is a bad idea to mix such complaints with any other comment you want to make as that will get deleted as well. I have edited your post, rather than deleting it, on this occasion to make sure you understand the situation.

CO2isnotevil, the problem has always been that "skeptical" arguments are not consistent with anything else. No alternative theory has been brought forth that accounts for the physics and the data. At best, "skepticism" as you define it is just a series of attacks launched from no theoretical position and designed to get rid of the narrative that the reality of GW forces (it is us and it is bad) but not at all establish a more accurate, socially-produced scientific understanding of climate.

In other words, you don't care about the science; you care about managing the spin--hence the nature of your comment.

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Moderator Response: [Dikran Marsupial] Please keep the discussion impersonal and on the science. As they say "don't wrestle a pig, you both get dirty, but the pig likes it"; if you think someone is not engaging in scientific discussion, the best policy is to simply ignore them.

One thing that seems certain in all this are these words from Dr. Trenberth's above post:

"we have observing systems in place that nominally can measure the major storage and flux terms but due to errors and uncertainty, it remains a challenge to track anomalies with confidence".

In Trenberth's original "Perspectives" paper published in Science Tracking Earth's Energy, he was clear that the "missing energy" he was discussing was "due to either inadequate measurement accuracy or inadequate data processing".

However, Dr. Trenberth often talks or writes as if there is some actual "missing energy" he expects to find one day, as opposed to tracking down measurement or processing errors, which may lead to confusion for some.

What Trenberth wrote in his original Science paper appears to place him very close to Hansen's view, i.e. that this is at present murky territory, except Hansen appears to be questioning how much heat models should be allocating to the deep ocean when Trenberth appears not to be.

Hansen says he thinks the Argo float system, if extended and maintained for the long term, added to other data on the smaller heat reservoirs, could provide "potentially accurate" data on Earth's energy balance, where it is less likely, in his view, that current or proposed satellites can.

Trenberth has written about the Argo system which, with some other fairly new items in the data collection arsenal, constitutes a "revolutionary" change in what scientists have available for analysis.

In the meantime, I think many are taking too much away from their reading of Dr. Trenberth. It seems to me he's using "missing energy" in the way particle physicists use the term, when their calculations involving the latest data prove to them, because nothing can be missing, that they're mistaken somewhere. Trenberth assessed the data available, added it up, and found what should not be able to be found if the data was complete and good, i.e., that something was "missing". He published his findings and went back to the drawing board, or computer model as it turned out.

Some seem to have problems with Dr. Trenberth's way of expressing himself. Most famously is the way his "missing energy" email was seized by deniers. But James Lovelock illustrates how badly someone can misunderstand Dr. Trenberth even if wilful distortion is not the goal. See Stewart Brand's online Afterword

In this Afterword, Brand quotes Lovelock telling him that after reading Trenberth's "missing energy" paper he decided that"something unknown appears to be slowing the rate of global warming", which caused Brand in his subsequent public speeches to describe a possibility that by 2050 "nothing" will have happened to Earth's climate. Further discussion of Brand's thought here Brand and Lovelock are wandering around touting the work of Garth Paltridge, specifically, this "sensible skeptic"s (Brand's words) book with its Foreword by Lord Monckton.

Dr. Trenberth is clear when he talks about whether when describing things using this "missing energy" concept it means he thinks global warming has stopped - "the AGW signature is not large enough to overwhelm natural variability and so the trend from increased GHGs is only clear on time scales of 25 or more years. We used 25 years in Chapter 3 of IPCC as the lowest trend we provided that was meaningful.... So any pause in sfc T increase from 2000 to 2008 is not unexpected and the first 8 months of this year were the warmest on record and have restored the upward trend. So there is no evidence of a reduction in trend" (personal communication).

P.S. There are some great graphics N.O.A.A. provides that may make it clearer to some who wonder what El Nino/La Nina a.k.a. ENSO is. Imagine we've sliced into the ocean so we can get a 3D view of its heat content at various times during the ENSO cycle:

Hansen describes ENSO as heat "sloshing around" in the planetary system. As the hotter water spreads out its heat is more available for transfer into the atmosphere. When the hotter water forms a deeper pool there is less surface area for heat to come out of it into the air. Since by far most heat entering the planetary system is going into the ocean, and it sloshes around like this, it becomes more apparent how El Nino/La Nina can influence the average global surface temperature chart in the way it appears to do.

Hansen's Bjerknes Lecture had a chart showing the correlation between El Nino/La Nina (depicted at the bottom of his chart) and the average global surface temperature chart depicted at the top:

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Response:

[DB] "Dr. Trenberth is clear when he talks about whether when describing things using this "missing energy" concept it means he thinks global warming has stopped"

"It is quite clear from the paper that I was not questioning the link between anthropogenic greenhouse gas emissions and warming, or even suggesting that recent temperatures are unusual in the context of short-term natural variability.

This paper tracks the effects of the changing Sun, how much heat went into the land, ocean, melting Arctic sea ice, melting Greenland and Antarctica, and changes in clouds, along with changes in greenhouse gases. We can track this well for 1993 to 2003, but not for 2004 to 2008. It does NOT mean that global warming is not happening, on the contrary, it suggests that we simply can't fully explain why 2008 was as cool as it was, but with an implication that warming will come back, as it has. A major La Niña was underway in 2008, since June 2009 we have gone into an El Niño and the highest sea surface temperatures on record have been recorded in July 2009."

I'm quoting from Dr. Trenberth, so are you, and the two quotes say just about identical things. What's the problem?

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Response:

[DB] I did re-read your comment. Your quote that I used in my response to you is the opposite of what Dr. Trenberth has up on his website, which I quoted. They are not identical. Or are you saying I misquoted you?

My quote of you:

"it means he thinks global warming has stopped"

My quote of Dr. Trenberth:

"It does NOT mean that global warming is not happening, on the contrary, it suggests that we simply can't fully explain why 2008 was as cool as it was, but with an implication that warming will come back, as it has."

No problem. Dr. Trenberth says global warming has not stopped, which is the opposite of your attribution of what he said.

I did not mean to say that Dr Trenberth believes or has ever said that global warming has stopped. I can agree that the words I used are confusing. Here's another attempt:

"Dr. Trenberth is clear that when he talks about "missing energy" he does not mean he believes global warming has stopped. Quoting from Dr. Trenberth:" Then follow with the quote I used.

Perhaps you could edit my comment and remove your objections? I never intended to be saying what you've both taken from my words.

I thought the conditional words in my sentence made things clearer than they obviously are, that's the "whether... it means" part. I set up the quote I used from Dr. Trenberth with this conditional, i.e. Dr Trenberth is clear about "whether... it means", then I let him speak for himself.

Dr Trenberth has generously given his time to answer queries by private email in the past - so if he is travelling in AU/NZ we can only hope he can find time to answer questions on this thread.

Regarding this quotation from above post:

"In the meantime, we have explored the extent to which this kind of behavior occurs in the latest version of the NCAR climate model. In work yet to be published (it is submitted), we have found that energy can easily be “buried” in the deep ocean for over a decade. Further preliminary exploration of where the heat is going suggests that it is associated with the negative phase of the Pacific Decadal Oscillation and/or La Niña events."

Without seeing the yet to be published paper, it seems this 'heat burial' would raise a number of further questions:

1. What is the physical mechanism for getting heat down into the deep oceans (below 700m? or 2000m?) in short time frames - a few years?

2. Over a decade - why not 2 or 3 decades or 50 years? Heat buried from prior to the 'official' start of AGW in 1975 could be re-appearing to warm the surface. Would that be caused by AG forcings or the Sun?

3. Again my question from #31 about whether the ENSO-La Nina cycles are 'internal' redistributions of global heat already within the system or are external global forcings which should be added to the RF and climate response terms to determine an imbalance?

Unless I am misreading the scale in DL #43 graphic - the depth of ENSO-LaNina 'sloshing of heat' is 300-600ft (100-200m)- hardly related to the deep oceans.

"[DB] Please do not rehash the entirety of the 2nd Law thread. You were painstakingly corrected there, many times, by patient commentators."

What is this supposed to mean? I don't even know what you're referring to, and I certainly don't expect Kevin to go sifting through various threads to answer questions. These issues have come up in many different threads, and I and others have been accused of being off topic addressing them, and it was suggested by many that we have a separate thread on it. Now there is finally a thread and we can't address the issues again?

Is this what your saying? If it's not what you're saying, perhaps you can clarify what it is you mean?

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Response:

[DB] It means what it says. Various learned individuals have tried to help you gain understanding but were thwarted by your insistence upon reality contorting itself to your personal interpretation of it. Quite frankly, everyone's patience has grown thin at the intransigence displayed. "Going there" yet again (both you and your mentor George White) even after being corrected is trolling.

I'd like to see Dr. Trenberth answer the question of how heat gets to the deep ocean and back again to "haunt us" in a matter of decades. Is this a new process his model shows now that the planetary system is this warm?

Dr. Joellen Russell was interviewed by Robyn Williams on The Science Show about her theory that the interaction of ozone depletion and global warming, by affecting the location and power of the Southern Westerlies, will affect the power of the Antarctic Circumpolar Current, which will drive more heat and CO2 into the deep ocean for many decades then shut off this primary driver of global ocean circulation.

Her models suggest that as the Westerlies move south and locate themselves more directly over the Antarctic Circumpolar Current they will drive it more intensely. Since this current is 4 times more poweful than the Gulf Stream and is the major driver of the exchange of water between the deep ocean and the rest of the global ocean, more heat and CO2 thus will go into the deep ocean, at least until it all stops. I'm not clear on why she says it all stops after a while.

On the other hand, Boning et.al. studied the Antarctic Circumpolar Current and found no evidence that it had strengthened although the Southern Westerlies have changed their location quite a bit already - they seem to think that the ACC might be as strong as it can get already and all additional energy will be dispersed as eddy currents.

But at this year's AGU Martinson described his observations of increased heat in the ACC and accelerated glacial melt in the Antarctic Peninsula.

Russell in her Science Show interview states that observations like what Martinson is making confirm her theory that the ACC is increasing in power.

I became interested in trying to understand all this but as you can see I didn't get that far.

If more heat and CO2 go into the ocean it will affect the average global surface temperature chart which so many seem to think is the prime indicator as to whether climate change is happening or not. I.e one of the big effects may be political. I think we've got to make the point more often that almost all heat is going into the ocean anyway, so this story of global warming is mostly about global ocean warming. It wouldn't take that great of a percentage increase in the amount of heat going into the ocean, because so much is going in already, especially if somehow what increased was only the heat going into the deep ocean, to make that global average surface temperature chart everyone thinks indicates whether the system is warming or not flatline, which would tend to cause even more political inertia than we are observing already.

One of many things I'd like to ask Hansen is does Russell's work affect his suspicion that current models overestimate how much heat goes into the deep ocean? Russell seems to be saying we've underestimated what is going on, and even if Boning hasn't observed it, Martinson's melting ice must have a cause.

One thing I'd like to ask Trenberth is what is his opinion of Russell's work.

The NOAA pix of ENSO I posted in a comment above are representations of TAO data, not ARGO, which go much deeper. I don't know if someone has come up with a graphic like that of what is going on using ARGO data for ENSO or for other ocean events. I put them up to illustrate the potential new data like ARGO represents, and also because those graphics helped me understand what ENSO is.